Which type of pesticide acts in gaseous form to kill pests when inhaled or absorbed?

Fumigants are a specific category of pesticides that operate in a gaseous state, making them particularly effective for controlling pests in enclosed spaces. They are designed to be inhaled by or absorbed through the surfaces of the pests they target. When fumigants are released into an environment, they diffuse throughout the area, penetrating cracks and crevices where pests may hide, allowing them to reach and eliminate pests that may not be accessible to other forms of pesticides.

This gaseous nature is key to their effectiveness, as fumigants can affect a wide range of pests, including insects, rodents, and even certain diseases caused by fungi. They are commonly used in situations such as the treatment of stored grains, structures like homes and warehouses, or soil disinfestation.

Other types of pesticides, such as contact pesticides, act by direct physical contact with pests, stomach poisons require ingestion by the pests to be effective, and systemic pesticides must be taken up by plants or organisms to have an effect. These mechanisms differ fundamentally from the way fumigants operate, highlighting why the correct response to the question is fumigants.